1. Field of the Invention
The present invention relates generally to the collection of human sweat for medical evaluation and is particularly directed to sweat collection devices.
2. Related Art
It is known that the concentrations of sodium and chloride are considerably above normal in the sweat of individuals suffering from cystic fibrosis. Sweat testing is routinely used to diagnose cystic fibrosis, particularly in infants, where such testing is often done between birth and about four weeks of age. In one method of sweat collection, as described in U.S. Pat. No. 4,542,751, incorporated herein by reference, sweating is induced in a substantially flat area of skin by pilocarpine iontophoresis, usually performed using an electrode with a substantially circular pilocarpine containing gel disc, as described in U.S. Pat. No. 4,383,529, incorporated herein by reference, and as manufactured by Wescor, Inc. of Logan, Utah, as a Pilogel® Iontophoresis Disc, placed over the skin of the individual to be tested where sweating is desired. A return electrode is placed on the skin near the electrode with the pilocarpine containing gel disc and a voltage is applied between the electrodes sufficient to cause current flow through the pilocarpine containing gel disc and into the skin between the electrodes. The pilocarpine molecules flow from the pilocarpine containing gel disc through and into the skin area in contact with the pilocarpine containing gel disc. When the pilocarpine iontophresis is complete, the electrodes are removed. The pilocarpine in the circular skin area that was under and in contact with the circular pilocarpine containing gel disc activate the sweat glands in that skin area so that sweating takes place in that skin area.
After removal of the electrodes, a sweat collecting device known as the Macroduct® Sweat Collector, manufactured by Wescor, Inc. of Logan, Utah, which has a concave underside sweat-collecting surface of circular cross section, is placed over the iontophoretically-stimulated area on the skin and the device is firmly strapped in place. Sweat secreted by the individual's sweat glands flows between the skin and the concave underside sweat-collecting surface of the sweat collector and into a micro bore sweat collector tube. After a sufficient volume of sweat has accumulated in the sweat collector tube, the sweat is expelled from the tube and tested for chloride, sodium, and/or total electrolyte content.
While the prior art Macroduct® Sweat Collector described in the above referenced U.S. Pat. No. 4,542,751 works well in collecting sweat from infants for most testing currently being done, producing and collecting enough sweat for some testing is sometimes a problem. Sweat for sweat testing is usually collected from the arm or leg of the patient being tested. Because of the small width of an infant's arm or leg, particularly when four weeks or less of age, the diameter, and therefore the cross sectional area, of the circular cross section of the iontophoresis creating electrode and the circular cross section of the sweat-collecting surface of the sweat collector are limited by the width of the arm or leg. This limits the size of the area of the infant from which sweat can be produced and then collected by the sweat collector.